Warranties clearly state detailed guidelines for installation and that, when not followed, it is voided. The professional provider is not only aware of manufacturer instructions, but there is also better communication between departments, stating any concerns or challenges you may have, so there is better safeguarding of your home. You’ll most likely end up spending more money.
Rooms have baseboards, moldings and other protrusions with which to handle. The less experienced installer may over-order, resulting in waste, unnecessary expense and an installation full of wrinkles, bumps, rolls and squeaky joints. Also, who will be ultimately responsible if the person installing gets injured on the job? Finally, ask questions about who does the installation and find out how many of your flooring types (i.e., hardwood, carpet, tile, etc.) they have done. Get fully detailed quotes and be sure the installers are licensed, insured and bonded.